1. Field of the Invention
The present invention relates to a sensor apparatus having a magnifying glass element held in a holder element. The magnifying glass element has a cylindrical portion and a superposed convex lens portion thereon which is rotationally symmetrical with respect to the cylinder axis. The sensor magnifying glass also includes a plotter coil, which is coaxial with the cylinder portion.
2. Brief Description of Prior Art
Sensor magnifying glasses of this type are used together with digitizing tables, for example, for determining the spatial location of points located on drawings on the digitizing table and for storing these coordinates electrically in a memory so they readily can be picked up.
Typically, the known sensor magnifying glasses have a housing forming the holder element, into which the magnifying glass element is set; the plotter coil is secured to the underside of the housing, i.e., the side that comes to rest on the digitizing table. The plotter coil is connected to a circuit arrangement in the housing, and on top of the housing actuating buttons are provided for controlling and triggering the various electrical functions.
The housing is typically made of nontransparent material, so that only in the area of the magnifying glass element itself is the user able to recognize details of the drawing underneath and make the appropriate alignment with respect to the cross-hairs in the magnifying glass element. The coil is located on the underside of the magnifying glass element and interferes with the view of the drawing underneath.